Pressure Head Research Articles

Effect of stress conditions on concentrated leak erosion resistant of fine-grained soils with different characteristics

AbstractInternal erosion is one of the most important factors that cause earth structures that retain water, such as embankment dams, to collapse. Concentrated leak erosion, one of the forms of internal erosion, occurs in cracked fine-grained soils and pressurized flow conditions. To evaluate the concentrated leak erosion risk of cracks/voids, it is necessary to ascertain the erosion resistance of these materials. The erosion rate and critical shear stresses determine internal erosion resistance in concentrated leak erosion. This study determined soil’s concentrated leak erosion resistance using test equipment that allowed the flow to pass through a hole with stress-free (no loading), anisotropic-compression stress, anisotropic-expansion stress, and isotropic stress conditions. The stresses that developed in the samples’ hole wall where erosion occurred were determined with numerical modeling as pre-experimental stress conditions. The experiments were performed under a single hydraulic head on four selected cohesive soils with different erosion sensitivity. Time-dependent flow rates obtained from the test system can be used to determine hydraulic parameters, such as energy grade lines, with the help of basic theorems of pipe hydraulics in theoretical hydraulic models. Moreover, the erosion rates were quantitatively determined using the continuity equation, while critical shear stresses were qualitatively compared for concentrated leak erosion developed by the dispersion mechanism. As a result of the experiments, stress conditions influence the concentrated leak erosion resistance in the soil samples with dispersive erosion. Moreover, the shear strength in the Mohr–Coulomb hypothesis can explain the erosion resistance in these soils under stress conditions depending on the sand/clay ratio.

Otolith morphometry and its role in determining the growth of Periophthalmus chrysospilos distributed in some coastal provinces in the Mekong Delta

This article first provided information on otolith shapes, the variation of otolith weight by sex, fish size, season, and sampling site, and the linear relationship between otolith weight and fish size. A total of 815 Periophthalmus chrysospilos specimens from Duyen Hai, Tra Vinh; Tran De, Soc Trang; Dong Hai, Bac Lieu; and Dam Doi, Ca Mau in the Mekong Delta ranged from 4.20 to 12.50 cm total length and from 1.26 to 16.88 g weight were analysed. The analysis results revealed that Ps. chrysospilos had a square otolith, deeply notched at the anterior apex and flat at the posterior apex. The weight of the left otolith showed a statistical difference according to survey factors, including gender, fish size, season, and sampling site. The otolith weight had a proportional relationship with to the total length, body weight, and head length of mudskippers (r2 =0.7~0.9), which meant that fish size could be predicted from the otolith weight and about 70-90% of the otolith weight of Ps. chrysospilos varied corresponded the growth of the fish.

Evaluation of Submergence Limit and Head Loss in Flow Measuring Flumes Using Flow-3D Predictive Modeling

Evaluation of Submergence Limit and Head Loss in Flow Measuring Flumes Using Flow-3D Predictive Modeling

Dynamic behaviour and energy dissipation of offline air pockets in transient pipe flows

ABSTRACT The traditional one-dimensional (1D) model often fails to accurately predict the dynamic pressure response of large offline air pockets during transients, due to a lack of comprehensive understanding of the underlying mechanisms of transient interaction with offline air pockets. This study investigated dynamic behavior and energy dissipation of offline air pockets through experiments and numerical models. Experimental pressure responses were predicted using a 1D-3D coupling model, which presented superior performance compared to traditional 1D model. The 1D-3D coupling model was further utilized to investigate the air-water interface, internal energy and turbulence distribution of offline air pockets. The results reveal that the stability of the air-water interface depends on the decelerating distance of the jet in offline tube, explaining the instability phenomenon with lower water levels observed in experimental snapshots. The internal energy pattern suggests different energy dissipation mechanisms compared to the inline air pockets. The distribution of turbulence intensity and effective thermal conductivity indicates significant additional energy dissipation at the inlet and outlet of offline neck. By incorporating a minor head loss term for offline neck into traditional 1D model, the pressure response aligns well with the results obtained from 1D-3D coupling model under different flow rates and air volumes.

Spatiotemporally non-stationary evolution of groundwater levels in Poyang Lake Basin driven by meteorological and hydrological factors

The complex relationship between wet-dry transition in the Poyang Lake basin and groundwater storage significantly affects the lake's hydrology, downstream ecological state, and overall security along the Yangtze River in China. There is, however, a notable lack of systematic exploration into how various factors drive spatiotemporal variability in groundwater level (GWL). Using local indicators of spatial association (LISA), spatial non-stationarity models, and multi-source data, our analysis explores the spatial distribution of GWL and quantifies the influence of driving factors on its spatiotemporal non-stationarity at annual and monthly scales. We also compare driving factor contributions in hilly, plain, and local areas within the Poyang Lake basin. Our findings reveal significant local clustering of GWL, indicating substantial spatial autocorrelation and geographic heterogeneity in GWL. Influencing factors exhibit non-stationary effects on GWL at spatial and temporal scales, with precipitation (P), ground surface elevation (GSE), and soil moisture (SM) being primary contributors, generally exerting positive effects. SM contributes most during dry years and normal periods. P and the Palmer Drought Severity Index (PDSI) have greater impacts in hilly areas, while GSE shows the opposite trend. Rainfall is a source of groundwater recharge, with a lagged response observed in GWL to rainfall in this basin. The lag time is about 1–2 months. Evapotranspiration is not the dominant discharge pathway. The decrease in GWL during the dry season is mainly due to reduced precipitation recharge and increased lateral groundwater discharge from areas of high hydraulic head to areas of low hydraulic head.

A comprehensive numerical study on heat transfer and friction characteristics of offset-strip fins

Offset-strip fins are among the most used geometries in compact heat exchangers. The geometric and flow parameters of the fins affect their heat transfer effectiveness and head losses. Hence, accurate predictive models are needed to guide the design process. However, most of the correlations available in the literature are valid only for a limited set of geometric configurations and flow regimes. This work discusses the derivation of multivariate response surfaces for the equivalent Darcy and Colburn factors in offset-strip fins. These surfaces feature clear applicability ranges and extend over wide Reynolds and Prandtl number ranges (50≤Re≤12000, 0.71≤Pr≤190). In addition, a novel empirical model for the Prandtl number scaling exponent is proposed. The analysis is carried out through a Design of Experiment approach, performed with computational techniques. Each numerical experiment is carried out by CFD analysis of a periodic fin geometry. The obtained response surfaces approximate CFD results with a mean deviation of ±8.4%. Moreover, application of the correlations to the analysis of complete heat exchangers issued mean and maximum deviations of ±7.8% and ±20%, respectively, thus highlighting the usefulness of the proposed models for the accurate modelling of offset-strip fins in heat transfer applications.

Flow in fracture Intersections: Deflection flow assumption reexamined

Deflection flow, which represents the process of flow redistribution at fracture intersections, is essential for accurately predicting fluid infiltration and contaminant transport in fracture networks. However, previous studies focused on the outcome of flow redistribution but neglected the process, leading to poor knowledge of deflection flow at intersections. In this study, numerical investigations of the deflection flow in cross fractures were carried out based on Navier-Stokes equations and the results were compared with previous experiments. Geometrical characteristics such as angle(φ), aperture ratio(k), and hydraulic characteristics like inlet flow ratio(n) were considered to explore the mechanism of deflection flow. The deflection flow intensity(Xφ) was introduced to characterize the magnitude and direction of the deflection flow. The results showed that the deflection flow is caused by unequal local head loss. The effect of φ on Xφ is limited by n and k. Increasing n or k enhances the deflection flow but the directions of the induced deflection flow are reversed. The obtained relationship was further supported by theoretical results derived from the cubic law. Subsequently, sensitivity analysis of impact factors to the deflection flow was carried out by the Morris method, the sensitivity in descending order was k, n, φ. Finally, based on the analysis of Xφ, the conditions to limit the occurrence of deflection flow was obtained as a linear positive correlation between the critical inlet flow ratio(nc) and aperture ratio(k). The results from this study may provide insights and physical constraints on construction of flow models based on discrete fracture networks.

Energy performance and pressure fluctuation in multi-stage centrifugal pump with floating impellers under various axial oscillation frequencies

A novel multi-stage centrifugal pump with floating impellers is gaining traction in energy systems because it easily links stages in series for varying high head requirements. However, the axial oscillation frequency of the floating impeller introduces uncertainties in the pump's energy performance and pressure fluctuation. To address these issues, a comprehensive analysis of multi-stage centrifugal pumps was conducted, utilizing a computational fluid dynamics simulation method that incorporats dynamic mesh and multiple reference frame techniques, validated through three experimental trials. The findings show that average head coefficient and average efficiency are not significantly affected by the axial oscillation of impeller, but that pressure fluctuations, efficiency, and head coefficient all show periodic variations that are connected to the frequency of impeller oscillation. The amplitude of variations in the head coefficient and efficiency could increase by as much as 112.3 % and 172.4 %, respectively, under the influence of impeller oscillations, thereby heightening the instability of pump operation. Trigonometric functions for the energy performance during impeller oscillations are proposed to facilitate rapid assessment of pump stability. This study offers valuable insights into the unsteady characteristics of novel multi-stage centrifugal pumps and serves as a reference for further understanding their dynamic behavior.

Improvement of field falling-head test and determination of hydraulic conductivity using Darcy’s equation

This study presents a novel permeameter design for field falling-head tests to determine vertical hydraulic conductivity (K) using Darcy's equation. The design features an open-ended standpipe with two ports for simultaneous measurement of hydraulic heads at both ends of the sediment column, enabling direct estimation of flow rate (q) and hydraulic gradient (i). Flow rate is calculated by differentiating the best-fit curve for water level change above the sediment, and the hydraulic gradient is derived from the head difference between the ports. Laboratory and field tests consistently demonstrated a strong linear relationship between q and i (R2 > 0.999), validating the applicability of Darcy's equation for this new permeameter design. The K values obtained using the proposed method matched those obtained using the Hvorslev equation method. Furthermore, the design allows for continuous measurement of heads after the falling-head permeameter test, facilitating the collection of time series data for the hydraulic gradient. When combined with a pre-determined K value, this enables calculation of time series for the seepage rate across the surface water/sediment interface. To demonstrate this capability, preliminary tests were conducted using commercially-available pressure transducers to monitor heads and obtain seepage time series. The results of these tests are also presented.

Simulating the effects of retreating Urmia Lake and increased evapotranspiration rates on the nearby unconfined aquifer

The unsustainable management of water resources along with climate change impacts have led Urmia Lake to severely shrink since 1995. To quantify the groundwater losses in the surrounding area and to avoid the future worsening of a yet worrying scenario a numerical model is needed. For this purpose, a transient state MODFLOW model (2000–2016) has been calibrated and validated versus hydraulic heads. Good model performances were obtained, allowing to accurately estimate the groundwater budget. MODIS dataset was employed to set up the numerical model to identify temporal and spatial extent of evapotranspiration. Evapotranspiration turned out to play a massive contribution in groundwater outflow showing an increasing trend over time. Several scenarios, considering a different way to implement recharge and evapotranspiration in the modelling routine were assessed. The role of the spatialization of the evapotranspiration extinction depth was investigated by averaging remotely sensed heterogeneous datasets over the model domain. No significant differences in model performance indicators were found. Moreover, a model scenario without human groundwater exploitation and land use change was considered. The results slightly differ from the groundwater budget calculated by the validated model and thus indicating the climate change as the major driver of groundwater depletion in the study area. The implementation of such a model allowed for the assessment of the exchange between the lake and the unconfined aquifer, providing a robust foundation for future sustainable management.

Theoretical evaluation of high-permeability wellbore skin effect on aquifer response under pumping

Skin zones with distinct hydraulic properties often form around wellbores during drilling operations. Conventional skin-factor models, developed for low-permeability (positive) skin, assume discontinuous hydraulic heads between the wellbore and aquifer. However, these models may be inadequate for high-permeability (negative) skin scenarios resulting from intensive well development. This study derives a new skin-factor approach for negative skin approaches based on the two-zone model approach. We derive a new skin-factor approach that maintains continuous heads between the wellbore and aquifer while allowing for discontinuous fluxes. Using Laplace and finite cos-Fourier transformations, we develop a groundwater flow model for aquifer pumping under a partially penetrating well, incorporating this new approach. An asymptotic expansion method is employed to obtain a large-time solution. The proposed model is also compared to the existing two-zone model. Sensitivity analysis reveals that high-permeability skin significantly affects drawdown, particularly when there is a sudden increase in porosity within the skin zone. This revised approach provides a more accurate framework for modeling various skin effects, offering valuable insights for groundwater management and well hydraulic modeling in both hydrogeology and petroleum engineering applications.

Design Emission Uniformity of Horizontal Tapered Drip Laterals from the Normalized Pressure Head Distribution Approach

Design Emission Uniformity of Horizontal Tapered Drip Laterals from the Normalized Pressure Head Distribution Approach

A stepwise optimization method for topology structure of fluid machinery network

A stepwise optimization method for topology structure of fluid machinery network

RANCANG BANGUN SISTEM PENDINGIN UNTUK MESIN BUBUT BV 20

The purpose of this study is to design and create a cooling system on the BV 20 lathe. The method used in this study is the design method by conducting direct design manufacturing based on the condition of the BV 20 lathe and designs by calculating the total head pump and pumping heading. The manufacturing process is carried out starting from the identification of working drawings and identification of components using existing tools or machines, ordering and procuring the market for other components. Then it can be produced a cooling system for a BV 20 lathe with a 3 watt pump. Keyword designs, cooling system, lathe BV 20

Direct filtration of low-turbidity water by fixed-bed ion exchange treatment

In drinking water treatment, low-turbidity water (e.g., < 5 NTU) is often purified by direct filtration comprising coagulation, flocculation, and rapid sand filtration. This study assessed the potential of replacing the rapid sand filter with a fixed-bed ion exchange column. Two types of anion exchange resins, polyacrylic (Purolite A860) and polystyrene (Purolite A502PS), were used in fixed-bed columns without preceding coagulation and flocculation. After the first use of the new resins (14-h operation), the A860 column showed more significant head loss buildup than the A502PS column (151 and 101 cm, respectively). This can be attributed to the effective size of A860 resins (0.38 mm), which was smaller than that of A502PS resins (0.52 mm). A860 resins were superior to A502PS resins in filtrate quality. The A860 resins achieved filtrate turbidity (0.16–0.26 NTU) lower than the A502PS resins (0.19–0.35 NTU). Similarly, dissolved organic carbon removal by A860 resins (25–37 %) was higher than that by A502PS resin (15–25 %) due to the low hydrophobicity of the feed water. Air scouring and water backwashing were ineffective in regenerating A860 resins. In contrast, cleaning with a NaCl solution (pH = 12) partially recovered the capacity of A860 resins for turbidity removal.

Suitability evaluation of an equivalent porous medium method for characterizing 2-D flow based on the fracture fractal dimension

ABSTRACT An equivalent porous medium (EPM) method is widely utilized in various practical applications of hydrogeological engineering with areas of a fractured geological medium (FGM). However, the suitability of the EPM model still lacks sufficient scientific evaluation when considering the distribution of water head and flow velocity. In this study, the suitability of the EPM model to the fractal dimension of a discrete fracture network (DFN) is analyzed based on numerical simulation experiments. The simulation results of the EPM model are compared with those of the DFN model. Then, a formula is proposed to evaluate the suitability of the EPM model for characterizing two-dimensional flow distribution. The results show that with the increase of the fractal dimension, the suitability of the EPM model decreases first and then increases, and the inflection point gradually appears in advance with the increase of the length–width ratio of the simulation domain. The length–width ratio of the simulation domain has a linear relationship with the suitability of the EPM model, and the slope increases with the increase of the fractal dimension. Finally, a quantitative evaluation method is proposed to calculate the suitability of the EPM model based on the fractal dimension and the length–width ratio of the simulation domain.

Effect of Micronutrients on Incidence, Damage Severity of Sucking Insect Pests of Sunflower and its Impact on Yield and other Arthropods

An experiment was conducted in a field on 23074/N latitude and 90035/E longitude at the central farm of Sher-e-Bangla Agricultural University, Dhaka, Bangladesh from November 2021 to April 2022. The experiment of eight treatments as follows: T1 = Urea @ 210 gm/plot + TSP @ 84gm/plot + MoP @ 98gm/plot [recommended doses (RD) of Urea, TSP and MoP] +Boron @ 7.0 gm/ Plot+ ZnSo4 @ 8.4 gm/ Plot ;T2 = RD of Urea, TSP and MoP +Spraying 0.2% Borax @ 2gm/ L of water; T3= RD of Urea, TSP and MoP +Spraying 0.2% ZnSo4 @ 2gm/ L of water; T4= RD of Urea, TSP and MoP +Spraying 0.5% Borax @ 5gm/ L of water; T5 RD of Urea, TSP and MoP +Spraying 0.2% Borax + 0.2% ZnSo4 @ 2gm/ L of water; T6 = Urea @ 210 gm/plot+ TSP @ 180 gm/plot+ MoP @ 150gm/plot + Spraying 0.5% ZnSo4 @ 5gm/ L of water; T7 = Urea @ 210 gm/plot+ TSP @ 180gm/plot+ MoP @ 150gm/plot+ MgSo4 @ 12 gm/ Plot and T 8= control. The experiment was laid out in a Randomized Complete Block Design (RCBD) with 8 treatments and 3 replications. The overall result indicates that the combination of different micronutrients decreased the incidence of sucking insect pests of sunflower and increased the abundance of beneficial arthropods compared to T8 treatment. In T1 treatment, the lowest leaf infestation percentage caused by aphid 17.49 and 19.50 %; Jassid 14.19 and 14.89 % and White fly 26.18 and 30.83 % at the vegetative and reproductive stages respectively. The highest number of beneficial arthropods per plot of lady bird beetle both adults and grubs ((3.63 and 5.53 respectively); honey bee (22.36), ant (3.55), spider (1.42) was also recorded in T1 treatment. The highest yield contributing characters of sunflower, the highest of head/ capitulam diameter (9.75cm), height of plant per plot (179.73 cm), leaf width (14.24 cm), leaf length (21.05 cm), area of leaves per plant (62.29 cm) and number of leaf per plant (21.93), number of total head per plot (29.83), number of seed per head (725.56), weight of single seed (1.03 mg), and weight of seed per head (54.96 gm) of sunflower were observed in T1 treatment which was statistically different from among all other treatments. The highest sunflower yield (1.92 kg /plot) and oil content (0.93 liter/2kg and 46.5%) were also observed from T1 treatment. Among the different micronutrient treatment combinations, different micronutrients using in T1 treatment were more effective for the reducing the incidence of sucking insect pests on sunflower. In the term of effect of micronutrients, T1= Recommended doses of Urea, TSP and MoP + Boron @ 7.0 gm/ Plot+ ZnSo4 @ 8.4 gm/ Plot; was an eco-friendly pest management practice for sunflower by which one can significantly reduce pest infestation without use of any chemical insecticides.

GIS analysis for the selection of optimal sites for mine water geothermal energy application: a case study of Scotland's mining regions

Water within flooded coal mines can be abstracted via boreholes or shafts, where heat can be extracted from (or rejected to) it to satisfy surface heating (or cooling) demands. Following use, water can be reinjected into the mine workings or discharged to a surface water receptor. Four criteria have been applied, using ArcGIS, to datasets describing mine workings and mine water below the Midland Valley of Scotland to provide an initial screening tool for suitability for mine water geothermal energy exploitation. The criteria are: (i) the presence of two or more worked coal seams below site; (ii) the absence of potentially unstable shallow (&lt;30 m) workings; (iii) a depth to mine water piezometric head of less than 60 m; and (iv) a depth of coal mine workings of less than 250 m. The result is the Mine Water Geothermal Resource Atlas for Scotland (MiRAS). MiRAS suggests that a total area of 370 km 2 is ‘optimal’ for mine water geothermal development across 19 local authority areas, with greatest coverage in North Lanarkshire. This result should not be taken to suggest that mine water geothermal potential does not exist at locations outside the identified ‘optimal’ footprint. The MiRAS does not preclude the necessity for specialist engineering and geological input during a full feasibility study.

PLANNING FOR THE DEVELOPMENT OF A DRINKING WATER DISTRIBUTION SYSTEM NETWORK IN SUNGAI PINYUH

The increasing water demand due to population growth and territorial expansion has significantly outpaced the natural water supply in Sungai Pinyuh, Kalimantan Barat. This sub-district, part of the Mempawah Regency, faces challenges such as insufficient access to clean water, deteriorating pipe infrastructure, and environmental pollution affecting water quality. To address these issues, a study has been undertaken to plan a comprehensive development of the drinking water distribution system in Sungai Pinyuh, guided by the Regional Regulation of Mempawah Regency No. 3 of 2014. The planning utilizes EPANET software, a tool developed by the U.S. Environmental Protection Agency (EPA), which allows for the simulation of dynamic conditions in the water distribution system. EPANET helps create detailed maps of the pipe network, determine pump and reservoir locations, and specify pipe characteristics. The software’s ability to simulate various scenarios, such as changes in demand or disruptions, is crucial for ensuring a reliable water supply. The analysis incorporates primary data from field observations and secondary data from population statistics and existing water supply documents. The proposed distribution system will employ HDPE pipes of various diameters and a pump with a capacity of 200 L/s and a head of 5 meters. Simulation results indicate that the system's velocity, ranging from 0.3 to 0.72 m/s, and other parameters, such as head loss and pressure, are within acceptable limits. Additionally, reservoir capacity planning is based on the maximum daily water demand, with a calculated capacity of approximately 3,347.839 m³ to ensure adequate supply. This study provides a strategic framework for improving the drinking water distribution system, addressing current deficiencies, and preparing for future needs.

Experimental study of hydrodynamics of groundwater flow in karst aquifers

ABSTRACT A large-scale laboratory model is constructed to simulate a karst aquifer. Three groups of experiments are conducted to study the matrix-conduit exchange and how head difference, conduit size, and matrix/conduit gradients affect it. The findings can be summarized as follows; (1) In experiments with higher matrix head, a counterintuitive head inversion, where conduit head becomes higher than matrix head, occurs when the matrix-conduit head difference is small (less than 9.3 cm and 11.5 cm for the 1-inch and 2-inch conduits, respectively); (2) Flow exchange is positively related to rescaled head difference (RSHD), a parameter combining the effect of matrix and conduit gradients and the matrix-conduit head difference; (3) When the conduit has the higher head, the flow exchange is on average 2.8 times higher than when the matrix has the higher head; (4) Doubling the conduit size doubled the flow exchange and increased the length of the head inversion.